Re: [Xen-devel] [PATCH 3/3] xen/arm: vpsci: Move PSCI function dispatching from vsmc.c to vpsci.c

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 26/01/18 18:27, Volodymyr Babchuk wrote:
> Hi,
Hi Volodymyr,

> On 26.01.18 20:15, Julien Grall wrote:
> > Hi,
> >
> > On 26/01/18 18:09, Volodymyr Babchuk wrote:
> > > On 24.01.18 20:34, Julien Grall wrote:
> > > > -    case PSCI_0_2_FN32(AFFINITY_INFO):
> > > > -    case PSCI_0_2_FN64(AFFINITY_INFO):
> > > > +    switch ( fid )
> > > >       {
> > > > -        register_t taff = PSCI_ARG(regs, 1);
> > > > -        uint32_t laff = PSCI_ARG32(regs, 2);
> > > > -
> > > > -        perfc_incr(vpsci_cpu_affinity_info);
> > > > -        PSCI_SET_RESULT(regs, do_psci_0_2_affinity_info(taff, laff));
> > > > -        return true;
> > > > -    }
> > > > -
> > > >       case ARM_SMCCC_FUNC_CALL_COUNT(STANDARD):
> > > >           return fill_function_call_count(regs, 
> > > > SSSC_SMCCC_FUNCTION_COUNT);
> > > Now definition SSSC_SMCCC_FUNCTION_COUNT depends on code in vscpi.c.
> > > Maybe it is time to introduce function get_psci_0_2_fn_count() and 
> > > use it there, what do you think?
> > Definitely not a function. It is a static number. But I can think of 
> > separate the call count.
> Yep, separate call count for vPSCI and for SSSC itself would be a good 
> thing.
Looking a bit more into it, this will not make a real improvement. This 
will be equally difficult to remember to update the call count.
Also, based on the recent SMCCC update (2.1.5 [1]):
"The General Service Queries for SMCCC call ranges are described in 
SMCCC section 6.2. These functions are not always well suited to 
firmware that is integrated with multiple sub-services being combined 
into one service range. For example, PSCI and SDEI in the Standard 
Service range. In particular, the ‘call count’ and ‘revision’ functions 
do not provide useful information to the caller when multiple functions 
are provided. As a result, these are not widely used to identify 
firmware services."
So I would not worry that much if the function count is not sync in the 
future. BTW, it is already wrong in Xen 4.10. For standard service, we 
don't implement 13 but 52.
Cheers,

[1] 
https://developer.arm.com/-/media/developer/pdf/ARM%20DEN%200070A%20Firmware%20interfaces%20for%20mitigating%20CVE-2017-5715_V1.0.pdf?revision=d20d1476-b770-4739-aebe-2d3147788e3f&la=en
I don't expect PSCI to be


--
Julien Grall

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